The present disclosure is related to the field of active signal transducers. More specifically, the present disclosure relates to the control of the transmission power of an active transducer.
Many monitored signals may be characterized as quasi-periodic signals. These signals exhibit a generally repeating wave form, but at a constantly changing frequency. One such example of a quasi-periodic signal is a returned ultrasound signal exhibiting a Doppler effect such as from the motion of a fetus' beating heart. While ultrasound signals have a variety of applications in medical and other fields, including imaging, diagnostic, and therapeutic applications, one such application is the use of ultrasound signals to monitor fetal heart rate.
In the measurement of fetal heart rate, it is desirable to be able to determine the instantaneous period of the fetal heart rate at each heart beat. The determination of beat-to-beat fetal heart rate can have additional diagnostic value in determining the condition of the fetus compared to evaluating fetal condition based upon average fetal heart rate alone.
When monitoring fetal heart rate, it is often desirable to use a mobile device, such that the pregnant mother may remain ambulatory while the condition of the fetus is being monitored. Portable fetal heart rate monitors must rely upon battery power such that the pregnant mother is not restricted in her movements by a connection to a more permanent power source.